Air-cooling Plants.
—The use of air-washing and humidifying plants so far mentioned has been confined to elimination of dust and the addition of moisture to air, under winter conditions. The same type of apparatus, used in summer, becomes a cooling plant, and by observance of the necessary requirements may be used to produce agreeable atmospheric conditions during hot weather.
When used for such purpose the air is washed, by passing it through falling water which frees it from dust and reduces its temperature. It is then further cooled by passing over cold surfaces that take the place of the heaters used in cold weather. The cooling surfaces are pipe coils kept cold by the contained water which comes from the water supply or from a refrigerating plant. The temperature and humidity are thus changed to suit the requirements of the conditioned air.
During the hot weather of summer the most disagreeable atmospheric condition is that caused by humidity near saturation, at a time of relatively high temperature. Under such conditions the cooling plant not only cools the air, but causes a precipitation of the moisture on the cold surfaces which are kept below the dew-point. The air is cooled and dehumidified to a point such that the conditioned air produces an agreeable atmosphere. The regulation of the degree to which the air is cooled is accomplished by the same general methods as are used in heating.